Sibelius 6 Automatic Rewriting?

Is there an easy way to change a section of a song in Sibelius from one note length to another? for example, a measure with 4 quarter notes would be converted to half a measure of 8th notes (and i'm not talking about the thing where you click the 8th not button so that it's a measure of alternating 8th notes and 8th rests).